FLOWABLE NETWORKS AS DNA-SEQUENCING MEDIA IN CAPILLARY COLUMNS

A novel class of materials that self-assemble in water into equilibriu m network structures with a well-defined mesh size consist of polyethy lene glycols (PEG's) end-capped with micelle-forming fluorocarbon tail s. These micellar systems form flowable aqueous gel-like networks that permit electrophoretic DNA sequencing in capillary columns. The gels have unusual rheological properties, including network breakdown under shear, resulting in plug flow that allows colums refill with complete ejection of byproducts of the previous sequencing analysis. In this s ystem, DNA fragment electrophoretic mobilities are unaffected by the h ydrophobicity of the polymer tails. Low molecular weight (M) PEG chain s (M 8000) show catastrophic resolution loss for DNA fragments larger than 100 bases due to band broadening. For a longer PEG segment (M 35 000) separating the end groups, band broadening occurs for DNA fragmen ts larger than 300 bases, implying that the PEG segment length control s the mesh size in the equilibrium network structure. Optimum sequenci ng results were obtained from a 6% solution of a 1:1 mixture of C6F13 end-capped- and C8F17 end-capped PEG 35 000. The resolution limit of f luorescent-dye-labeled sequencing products in this formulation was 450 bases in 75 mu m capillaries at 200 V/cm.